Handbook for Evaluating Emissions and Costs of APUs and Alternative Systems (2012)

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D-1 A p p e n d i x d 1. Question: Why should an airport implement an alternative system? Answer: An alternative system can help reduce airport emissions, resulting in improvements to local air quality. Airport Emission Reductions Credits (AERCs) can be issued for clean infrastructure projects under the FAA’s Voluntary Airport Low Emissions program. AERCs can potentially be used to offset emissions associated with planned capital improvement projects in the context of National Environmental Policy Act (NEPA) assessments and Gen- eral Conformity evaluations. When alternative systems are available, airlines can reduce APU usage, thereby reducing fuel consumption and overall APU maintenance. 2. Question: Can an airport operator and one or more airlines pool resources to implement an alternative system? Answer: Yes, airlines and the airport operator can jointly fund the construction of alternative systems. An important consideration in such cases is how the systems will be managed if an airline decides to leave the airport. 3. Question: What are the pollutants of concern emitted by APUs and alternative systems? Answer: APUs and alternative systems emit both criteria pollutants (e.g., CO, NOx, SOx, etc.) as well as greenhouse gases (e.g., CO2). Criteria pollutants emitted by APUs at the airport contribute to the degradation of local air quality near the airport. The use of alternative sys- tems effectively transfers the emissions of criteria pollutants to off-site power plants which are not considered in local airport air quality assessments. In contrast, greenhouse gases emitted by both APUs and power plants need to be accounted for when greenhouse gas emissions assessments are conducted in support of climate action plans and related studies. 4. Question: What are the impediments to implementing an alternative system? Answer: There are several potential factors that may impede the implementation of an alter- native system, but the most significant is usually cost. The airport operator and/or airlines will need to carefully consider their needs with the pros and cons of POU and central systems. 5. Question: How is the implementation of an alternative system usually funded? Answer: Funding has been obtained from a mixture of PFC programs, AIP grants, GARBs or other bonds, and more recently, through the FAA’s VALE program as well as privately funded programs (e.g., airline-driven). 6. Question: What type of alternative system is best for smaller airports? Answer: In general, there is no solution that is always best for smaller airports. As with larger airports, there are many factors that need to be taken into account including available fund- ing level, number of gates involved, aircraft types serviced, etc. With that in mind, smaller Frequently Asked Questions

D-2 Handbook for evaluating emissions and Costs of ApUs and Alternative Systems airports usually correspond to lower levels of funding, lower number of gates, smaller air- craft types, etc. In such cases, depending on how small the facility is, POU and portable diesel-powered systems may be better than central systems. 7. Question: What are the cost differences between different alternative systems? Answer: POU systems generally have much lower up-front capital costs while central sys- tems are generally more efficient and have longer-lasting components which results in lower operating and maintenance costs. The overall cost differences can be determined using a life-cycle cost assessment but will depend on various factors including the number of gates affected, aircraft types serviced, the expected service lives of the systems, etc. 8. Question: What are the differences between the APU emissions calculation methodology presented in this handbook versus the method used in the FAA’s Emissions and Dispersion Modeling System (EDMS) and/or Aviation Environmental Design Tool (AEDT)? Answer: The methods are similar in that they both involve the multiplication of activity data with emission factors to calculate emissions. However, the source, form, and resolution of the datasets are significantly different. The FAA’s EDMS/AEDT uses single, average emission factors (kg/hr) for each APU that were obtained from various sources including the USEPA. In contrast, the Handbook uses data from the Swedish Defense Research Agency (FOI) which represent the latest set of measured data for different power settings as a function of fuel flow (g/kg fuel). Although the Swedish FOI data suffices for the five aircraft categories used in the Handbook, the EDMS/AEDT has a more comprehensive dataset (covers more APU types). 9. Question: What type of alternative system is best for large busy airports with many passenger boarding gates? Answer: In general, there is no solution that is always best for larger airports. As with smaller airports, there are many factors that need to be taken into account including available fund- ing level, number of gates involved, aircraft types serviced, etc. With that in mind, larger airports usually correspond to higher funding levels, higher number of gates, larger aircraft types, etc. In such cases, unless the flexibility of a POU system is desirable, the efficiencies and longer-lasting components may make central systems a better choice for long term cost savings. The more gates that are involved, the more savings are realized. 10. Question: Who is responsible for APU emissions? Answer: For greenhouse gases, airlines are responsible if using a strict ownership defini- tion. As such, the emissions would be listed under the Scope 1 category within the World Resource Institute’s (WRI’s) protocols. This would mean that the airlines also could receive credit for any reductions in these emissions. However, from a control standpoint, an airport operator could argue that the influence (control) it can exert over the tenants (airlines) in reducing their APU emissions through the use of alternative systems would entitle the air- port operator to receive the reduction credits, especially if the airport operator also funded the implementation of the alternative systems. This is an evolving issue. For criteria pollut- ants, the responsibility is project-based and usually that of the airport operator. The airport operator is responsible for accounting for APU emissions in its emission inventories as well as being able to claim credits for APU emissions reductions. 11. Question: Can an airport operator require an airline to use an alternative system? Answer: Yes, as a tenant, an airline is subject to the rules and requirements set forth by the airport operator. However, this does not ensure compliance as an objecting airline has the right to leave the airport. Also, in practice, airlines and their employees may not always obey such a requirement especially if the airport operator is lax in enforcing it.

Frequently Asked Questions D-3 12. Question: Which alternative system is better—POU or central system? Answer: Each of these systems has advantages and disadvantages. POU systems offer flex- ibility since each system is self-contained and can be added, modified, or removed without impact to other systems. POU systems have relatively low capital costs. In contrast, central systems have higher capital costs and less flexibility, but offer greater efficiencies and more durable components that result in lower operating and maintenance costs as well as longer life spans. 13. Question: Will the use of alternative systems (as opposed to using APUs) reduce emissions and noise? Answer: In general, the use of alternative systems will reduce both noise and emissions. While criteria pollutant emissions would still occur at electric power plants, they are esti- mated to be significantly lower than what the APUs would have produced. Greenhouse gas emissions at the power plants are also predicted to be significantly lower. Noise levels gen- erated by the electrical components of alternative systems are much lower than APU noise levels, while air handling units (AHUs) can generate similar noise levels to APUs. 14. Question: Can the emissions calculations in this Handbook be used to satisfy VALE and NEPA requirements or greenhouse gas emissions evaluations? Answer: No. The Handbook and its components are only to be used for planning purposes. 15. Question: How do you assess emissions for aircraft that remain overnight (RON) at a gate location? Answer: To conduct this assessment, the total usage times for either the APUs or alternative systems will need to be estimated. It should be noted that if APUs are used, they will likely be shut off during the night while alternative systems may be used throughout the night. The total usage time should be split between the “Gate In” and “Gate Out” modes based on the distribution of the default TIM values for these modes. It is recommended that unless actual data is available, the default TIM values for the “APU Start” and the “Main Engine Start” modes be used.